A thin film composite (TFC) membrane is a membrane that has layers of dissimilar materials joined together to form a single membrane. This layered construction permits the use of material combinations that optimize performance and durability of the membrane.
TFC membranes are used for nanofiltration, and in reverse osmosis and forward osmosis membranes for treating tap water, brackish water and sea water. Such membranes typically are made by interfacial polymerization of a monomer in a nonpolar (e.g., organic) phase together with a monomer in a polar (e.g., aqueous) phase on a porous support membrane. TFC membranes are used where flux and substantial rejection characteristics are required, e.g., in the purification of water. Various materials and chemical additives have been added to TFC membranes to increase flux without reducing rejection characteristics and have met with limited success. Such membranes are also subject to fouling resulting in reduced flux as contaminants, e.g., material from the brackish or seawater to be purified, build up on the surface of the TFC membrane.
What are needed are chemical additives that can be added, particularly additives that can be dissolved in the organic phase, during membrane formation that result in membranes with improved flux while having negligible negative impact on salt rejection, or maintaining or improving salt rejection characteristics, as well as methods for preparing such improved TFC membranes.